Decoupled Control of CO2 and Nitrate Reduction Intermediates to Enable Efficient Tandem Urea Electrosynthesis

Abstract

The direct electrochemical coupling of CO₂ and nitrate (NO₃^–) offers a sustainable alternative to the energy-intensive Bosch–Meiser process for urea synthesis. However, achieving efficient C–N coupling at single active sites remains challenging due to the kinetic mismatch between CO₂ and NO₃^– reduction, as well as the intricate multistep proton-coupled electron transfer process. Here, we present a sacrificial template-based strategy to synthesize a two-dimensional (2D)/zero-dimensional (0D) FeP_0.9S_2.9–x/Ag₂S heterostructure catalyst, enabling the tandem coreduction of CO₂ and nitrate for urea electrosynthesis. Electrochemical studies, in situ measurements, and theoretical calculations together demonstrate that the heterostructures with strongly coupled interfaces not only modulate the electronic structure but also enable decoupled control over NO₃^– and CO₂ reduction. FeP_0.9S_2.9–x offers a moderate conversion rate from NO₃^– to ammonia, generating *NH₂ intermediates while mitigating overhydrogenation to ammonia. Meanwhile, Ag₂S with optimized loading facilitates efficient conversion of CO₂ to CO, enabling the diffusion and electrophilic attack of CO on *NH₂, thereby forming the critical *CONH₂ intermediate for urea production. As a result, the FeP_0.9S_2.9–x/Ag₂S tandem catalyst achieves a high urea yield rate of 1160.9 μg h^–1 mg_cat^–1 with a Faradaic efficiency (FE) of 15.4% at −0.7 vs reversible hydrogen electrode, outperforming the individual FeP_0.9S_2.9 nanosheets and Ag₂S nanoparticles. This study provides key insights into the rational design of heterostructure catalysts that exhibit strong interfacial interactions and allow for decoupled control over parallel reactions to enhance complex coupling processes.